Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely new behavioral context the annotations lack: the metered pricing model (daily free allowance, then $0.001 USDC via x402), which affects how an agent should budget calls.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with no padding, and the resource identification leads. The awkward first clause slightly blurs the opening but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be described, and the schema fully covers the single parameter. However, for a lookup-by-code tool there is no mention of invalid/missing code behavior, and the purpose statement is too imprecise to tell the agent what it will actually get back.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with a single 'area' parameter documented as 'Flood area code'. The description adds nothing beyond that (no format, prefix, or valid-code hints), so the baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The opening clause is garbled — it looks like a list of return fields (description, river or sea, polygon reference) rather than a statement of purpose — but 'for one flood area' implies a single-area lookup by code. It does not distinguish itself from siblings such as uk-flood__flood-areas-near or uk-flood__warnings, so an agent must infer the difference.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance, no prerequisites, and no mention of the sibling flood tools. The only conditional information is billing ('free within the daily allowance, then $0.001 USDC per call'), which is a cost note, not usage guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.